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Orange County Coastal Regional Sediment Management Plan APPENDIX B – HABITAT/BIOLOGY Direct, indirect, or cumulative impacts to biological habitats and resources may result from regional sediment management (RSM) activities. Direct impacts are “caused by the action and occur at the same time and place” (40 Code of Federal Regulations Sec. 1508). Examples of direct impacts include burial or removal of softbottom, benthic invertebrates during sand placement or dredging/excavation, respectively. Direct impacts also may occur to invertebrates and fish that become entrained with water that is removed or pumped during dredging operations. There also may be the potential for direct impacts to managed species, if present in the construction area. Generally, sandy beach invertebrate assemblages recover within one year or less, but may take longer if disturbance impacts highly diverse communities, long-lived species, repetitive disturbances occur before recovery is complete, or source materials substantially differ Direct Types of Impacts from Sediment Management Activities • Equipment (anchors, pipelines, vehicles) damage to habitats, injury of species. • Discharge burial of habitat and invertebrates. • Dredge removal of habitat and invertebrates. • Dredge entrainment of invertebrates and fish. Indirect • Invertebrate forage reduction. • Disturbance or interference (noise, lights, equipment) of wildlife movement or migration. • Turbidity effects (reduced photosynthesis, feeding, growth, or mortality). • Sedimentation effects (reduced photosynthesis, recruitment, nutrient stimulation, or mortality). • Enhanced sandy beach habitat and supported resources Source: SAIC 2011b from existing sediment (reviewed in SAIC 2011a). Subtidal invertebrate recovery takes one to three years depending on water depth and environmental conditions. Indirect impacts are “caused by the action and are later in time or farther removed in distance, and may include ..... related effects on water and other natural systems, including ecosystems” (40 Code of Federal Regulations Sec. 1508). Indirect consequences of direct impacts to benthic organisms are reduction in forage for wildlife, the duration of which relates to benthic recovery rates. Waters are indirectly impacted by sediment disturbance or placement, primarily resulting in a temporary decrease in water clarity (turbidity); however, changes to water chemistry also may occur depending on the characteristics of the sediments. Indirect impacts to nearby invertebrates, fish, birds, marine mammals, or vegetation have the potential to occur at distances within a few hundred feet to over one mile from effects such as equipment noise, turbidity, sedimentation (settlement of suspended sediment), or sand transport away from a receiver site due to waves and tides over time. Direct and most indirect impacts are associated with the construction phase of sediment management. Impacts of potential concern during the construction phase include (NRC 1985, 1995): Everest International Consultants, Inc. B.2
Orange County Coastal Regional Sediment Management Plan • Removal and/or damage to sensitive habitats and/or resources from equipment operation (dredges, pipelines vehicles, vessels), sand placement, or sand removal; • Disturbance and/or interference with movement, foraging, and/or reproduction of sensitive species from equipment operation (noise, disturbance); and • Persistent turbidity or water quality changes that interfere with foraging, respiration, recruitment, or reproduction of sensitive species or degrade vegetated habitats. • Potential for release of contaminants and adverse effects on aquatic animals. After sand placement or removal, the primary indirect impact relates to the recovery rate of invertebrates, which represent important forage for fish and birds. Important considerations of recovery rates include the relative change in sediment and habitat quality relative to existing conditions and project timing. Invertebrates seasonally recruit to beaches; therefore, recovery may be promoted by conducting projects outside the spring-summer peak productivity period. Recovery of subtidal invertebrate assemblage may be promoted by minimizing changes in sediment, hydrodynamics, or water quality within dredged areas (SAIC, 2011b). The primary indirect impact concern of sand migration from the receiver site is the potential to degrade sensitive habitats, if nearby. Impacts of potential concern after construction include: • Alteration of sediment, hydrodynamics, or habitat quality that delays invertebrate recovery rates; • Turbidity, sedimentation or sand migration that degrades nearshore reefs or vegetated habitats of particular concern (HAPCs); • Sand migration that increases the frequency or volume of maintenance dredging or excavation in nearby bays, creeks, or harbors. Cumulative effects are the "impact on the environment that results from the incremental impact of the action when added to other past, present, and reasonably foreseeable future actions ...” (40 Code of Federal Regulations 1508.7). The area of potential effect may occur in the Plan area over time due to repeated effects from an action in the same area, additive effects from multiple impact sources, or a combination of effects taking place slowly over time (Peterson and Bishop, 2005). RSM planning provides opportunity to increase the regional effectiveness of beneficial use of maintenance dredged materials, opportunistic upland sand sources, and offshore dredging and beach nourishment projects. Because RSM activities involve repetitive beach nourishment and dredging in certain areas, the potential for cumulative impacts is an anticipated issue of concern. Avoidance of repetitive disturbance within the same Plan area within the same year is recommended to promote recovery of the invertebrate prey base and minimize cumulative impacts. Establishing a geospatial database to track projects, sediment quantities, and frequency of implementation would facilitate assessment of potential cumulative impacts on the basis of both geographical (e.g., percentage of planning area affected) and temporal (frequency) scales of Everest International Consultants, Inc. B.3
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